1. Field of the Invention
This invention generally relates to suspension systems for motor vehicles. More specifically, the present invention relates to an adjustable attachment for securing a stabilizer bar to a vehicle.
2. Disclosure Information
Torsional stabilizer bars have proven useful in vehicles for many years. Such stabilizer bars commonly incorporate a transverse torsion bar segment pivotally attached and interconnecting the vehicle chassis and suspension components. Stabilizer bars generally operate to increase the roll stiffness of the vehicle and improve the steering stability of the vehicle by resisting differential movement of laterally opposed wheels relative to the vehicle chassis. One example of a stabilizer bar is shown in U.S. Pat. No. 4,648,620, which is assigned to the assignee of the present invention. Ford Motor Company Shop Manual for a 1991 model Mustang automobile shows a stabilizer bar mounted at the front suspension at p.14-05-5, and a stabilizer bar mounted at the rear suspension at p.14-05-5.
One of the drawbacks inherent in any suspension system is friction between moving suspension components connecting the wheel to the chassis. A particularly undesirable ride and noise characteristic can be related to the "static" friction of the suspension system. Static friction is best characterized by the amount of force necessary to initiate suspension movement on a stationary vehicle under curb load. Curb load defines the standard design payload for the vehicle, including a predetermined amount of fuel, passengers, and cargo.
Stabilizer bars may contribute to the static friction component in the suspension. Engineers typically design stabilizer bars so there is no load on the stabilizer bar when the vehicle is stationery at curb load. This is referred to as the neutral position. If there is any load in the stabilizer bar under this condition, it is referred to as pre-load. Pre-load reacts throughout the suspension, possibly causing binding in the suspension joints or increasing the static friction and tilting the vehicle from side-to-side.
FIG. 1 shows a motor vehicle 10 with a front suspension 12 utilizing a stabilizer bar 14 attached in a conventional fashion. Brackets 16 support the central portion of the stabilizer bar 14 from the chassis 18 while fixed length links 20 connect the ends of the stabilizer bar 14 to suspension members 22. However, the chassis 18, suspension members 22, and stabilizer bar 14 and the respective attachment points are built to specified design tolerances. In order for the stabilizer bar to be installed in the vehicle in the neutral position, the mounting points on the chassis 18 and the suspension members 22 must be co-planar with the plane defined by the mounting points of the unloaded stabilizer bar 14. Understanding the principle that three points defined a plane and the fact that there are four attachment points, combined with the manufacturing variations of each point, it can be seen that these planes are rarely co-planar. Therefore, the stabilizer is pre-loaded by various amounts when it is installed in the vehicle in the neutral position. In addition to affecting the friction in the suspension, this pre-loaded condition may also cause the chassis to tilt from one side of the vehicle to be at a different height than the other when the vehicle is at rest.
Designers have employed various means to reduce the undesirable friction in the suspension system. One example is that shown in previously mentioned U.S. Pat. No. 4,784,406, in which the stabilizer bar attaches to a MacPherson strut such that when the wheels of the suspension go into a jounce position the stabilizer bar exerts force against the strut in a direction tending to minimize friction within the strut. The design, however, does not teach reducing static friction in any other suspension components.
In order for stabilizer bar having more than three attachment points to be installed in a neutral position, the additional attachment points must fall within a single plane defined by any three of those points. Furthermore, that plane must be co-planar to the plane created by any three of the four corresponding attachment points on the vehicle. Attaching the stabilizer bar in accordance with the present invention minimizes the preload in the stabilizer bar by automatically insuring the stabilizer bar is in a neutral position at curb load. This, in turn, reduces the operating friction of the suspension system to which the stabilizer bar is attached and prevents the stabilizer bar from forcing the vehicle into an tilted condition.
It would be desirable to provide an apparatus for insuring the neutral installation of a stabilizer bar to substantially reduce the static friction imposed on the suspension system.